Characteristics of magnetosheath plasma in the vicinity of the high-altitude cusp

The gas dynamic and global MHD models predict magnetosheath plasma and magnetic field properties near the magnetopause. Because of the way the models include the magnetic field, predictions from gas dynamic theory and MHD simulations will differ in regions and under conditions when the magnetosheath magnetic field plays an important role. This paper compares predictions from the gas dynamic model and an MHD simulation with observations from Interball Tail and Polar in the vicinity of the high-latitude magnetopause and cusp during a period of strongly northward IMF. In this region and under this condition, the magnetic field plays an important role in the process of plasma depletion and magnetic reconnection. All plasma characteristics except one are found to deviate in predictable ways from the gas dynamic model and are found generally to be more consistent with the MHD simulation. The notable exception is the plasma bulk flow velocity observed at the spacecraft nearest the noon–midnight meridian.